Centrifugal countercurrent separator having bands covered with fluorocarbon sheets

ABSTRACT

A device which may be a centrifugal countercurrent exchange extractor and/or a centrifugal separator, has a cylindrical rotor within which are mounted concentric, radially spaced, cylindrical, apertured bands. The inwardly facing surface of each band is covered with an apertured fluorocarbon sheet such that the apertures in the sheets are respectively aligned with the apertures in the bands. Rivets pass through the aligned apertures and are deformed to hold the sheets securely against the bands. Orifices are provided either in rivets or through the bands and sheets for the countercurrent flow of liquids.

Elite States Patent [1 1 Doyle et a1. Nov. 6, 1973 1 CENTRIFUGALCOUNTERCURRENT 3,079,069 2/1963 Thylefors 233/20 R SEPARATOR HAVINGBANDS COVERED 9/1971 Simon 233/46 WITH FLUOROCARBON SHEETS Inventors:Collin M. Doyle; Wladzia G.

Podbielniak Doyle, both of 21 West Elm St., Chicago, Ill. 60610 Filed:Feb. 25, 1971 Appl. No.: 118,806

11.5. CI. 233/15, 233/31, 233/1 E Int. Cl B04b 15/02 Field of Search233/20 R, 31, 37,

References Cited UNITED STATES PATENTS 7/1970 Todd 233/15 10/1963 Doyle233/15 4/1959 Whitehead et al 233/27 9/1963 DiBenedetto 233/1 E PrimaryExaminer-James R. Boler Assistant Examiner-George H. KrizmanichAttorny-Prangley, Clayton, Mullin, Dithmar & Vogel [57] ABSTRACT Adevice which may be a centrifugal countercurrent exchange extractorand/or a centrifugal separator, has a cylindrical rotor within which aremounted concentric, radially spaced, cylindrical, apertured bands. Theinwardly facing surface of each band is covered with an aperturedfluorocarbon sheet such that the apertures in the sheets arerespectively aligned with the apertures in the bands. Rivets passthrough the aligned apertures and are deformed to hold the sheetssecurely against the bands. Orifices are provided either in rivets orthrough the bands and sheets for the countercurrent flow of liquids.

2 Claims, 5 Drawing Figures CENTRIFUGAL COUNTERCURRENT SEPARATOR HAVINGBANDS (IOVERED WITH FLUOROCARBON SHEETS BACKGROUND OF THE INVENTION Thisinvention relates to a device which may be a centrifugal countercurrentexchange extractor or a centrifugal phase separator, or a deviceconvertable from one form to the other. Both devices are characterizedby a cylindrical rotor containing a plurality of apertured cylindricalbands. When such a device is used as a countercurrent exchange device,the heavy liquid is introduced into the rotor near the axis thereof andthe light liquid is introduced near the periphery of the rotor. As therotor spins, the light liquid flows inwardly toward the axis while theheavy liquid flows outwardly toward the periphery with intimate mixingtaking place in the apertures. Precipitous solids which may be presenteither in the heavy liquid or in the light liquid tend undesirably tocollect and adhere to the inwardly facing surfaces of the bands. Thusthe bands must be periodically cleaned to remove the solids adheredthereto. Similar difficulties occur when the device is constructed to bea centrifugal separator. In that egent, liquid containing the two phasesto be separated is introduced at a point along the radius of the rotordetermined by the ratio of the light phase to the heavy phase. Thecentrifugal force operates on the liquid to separate the two phases,with the bands serving as coalescent areas which assist in theseparation process. Any solids present in the liquid undesirably tend toadhere to the inwardly facing surface of the bands.

There has been a previous proposal to reduce the amount of solids whichcollects on the inwardly facing surfaces of the bands. Such a proposalis shown in a patent issued to D. 8. Todd for Solids HandlingCentrifugal Extractor, U.S. Pat. No. 3,519,199. The patent discloses aprocess of spraying a thin film of Teflon (Du Pont trademark) on thebands (referred to in the patent as contacting elements) The bands arethe heated to a temperature of about 725 to 800 F. to bake or fuse thecoating. The Teflon repels the solids, thereby preventing them fromaccumulating on the bands.

It is desirable that the material used to construct the bands haveoptimum corrosion resistance so as not to be damaged by the highlycaustic materials which are often processed in centrifugal devices.Stainless steel type 316 is perhaps one of the most corrosion resistantmaterials presently available, due to the physical properties impartedto it during heat treatment. The chemical constituents of type 316stainless steel are chrmiurn, nickel, iron, molybdenum and carbon. Whenthese elements are properly proportioned, alloyed into steel andsubjected to an elevated temperature, carbides are formed. The steel isthen quenched rapidly so that the carbides are retained. These carbidesprovide the excellent corrosion resistant capability of type 316stainless steel.

lt type 316 stainless steel is heated to temperatures exceeding 500 F.,the carbon in the carbide precipitates to the grain boundaries, therebydiminishing the corrosion resistance of the steel. Since the process andconstruction disclosed in the Todd patent require heating totemperatures between 725 and 800it would not be usable with type 316stainless steel.

SUMMARY OF THE INVENTION It is, therefore, an important object of thepresent invention to provide a device which may be a centrifugalcountercurrent exchange extractor and/or a centrifugal separator whereinsoldis moving with the heavy phase do not tend to collect on theconcentric bands of the device.

Another object is to apply a fluorocarbon sheet to the bands in such adevice without theuse of heat.

Still another object is to provide a fluorocarbon sheet on the inwardlyfacing surface of each band in such a device, secured with rivets.

In connection with the foregoing object, it is yet another object toprovide rivets with orifices for passage of the liquids.

In summary, there is provided a centrifugal device comprising a shaft, arotor carried by the shaft and having a cylindrical shell, a pluralityof radially spaced cylindrical apertured bands mounted in the rotor, aplurality of cylindrical fluorocarbon sheets respectively against theinwardly facing surfaces of at least some of the bands, each of thesheets having apertures therethrough which are respectively aligned withthe apertures on the adjacent one of the bands, and a plurality ofrivets respectively passing through some of the aligned apertures on thebands and the sheets, each of said rivets being deformed at the endsthereof to hold the sheets respectively in intimate contact with thebands.

Further features of the invention pertain to the particular arrangementof the parts of the centrifugal device and the fluorocarbon coveredbands used therein whereby the above outlined and additional featuresare attained.

The invention both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification when taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a veiw in vertical sectionof a centrifugal FIG. 3 is a view in vertical section on a greatlyenlarged scale along 3-3 of FIG. 1;

FIG. 4 is a view in vertical section along 4-4 of FIG. 3; and

FIG. 5 is a fragmentary view taken along 5-5 of FIG. 3.

Referring now to the drawings, and more particularly to FIGS. 1 and 2thereof, there is shown a centrifugal countercurrent exchange device 10.The device 10 comprises a base 11 which may be secured to the floor bymeans of bolts 13. Attached to the base 1 l by means of hinges 14 is apart-cylindrical cover 15 which, in turn, carries a handle 16. Formedrespectively in the side walls 12 of the base 11 are axially-alignedopenings 17 within which is mounted the outer race of a pair of bearingunits 18. The inner race of each of the bearing units 18 is affixed to ashaft 30 which passes through the openings 17. The shaft 30 ismaintained in a fixed axial position by means of a pair of key members19.

Encircling the shaft 30 adjacent the ends thereof and alignedrespectively with the openings 17 are caps 20. One side of theshaft 30is provided with a sleeve 21 upon which is mounted a plurality of drivebelts 22. Each of the drive belts 22 may be connected to a motor ofdifferent operational speed, so that the speed of rotation of the shaft30 may be selected, depending upon the particular use of the device 10.

The shaft 36 is provided with a longitudinal bore on the left, as viewedin FIG. 1, within which is mounted a tube 31. The annular space betweenthe tube 31 and the shaft '36 defines a passageway 32 for the flow oflight liquid out of the device 10. The space within the tube 31 definesa passageway 33 for the flow of heavy liquid into the device It). Thetube 31 communicates with an inlet pipe 34 which is, in turn, coupled toa source of heavy liquid. An outlet pipe 35 communicates with thepassageway 32 and is coupled to a container or the like to collect thelight liquid effluent discharged from the device 10. The passageway 32communicates, adjacent its inner end, with a set of openings 36, and thepassageway 33 communicates, at its inner end, with a set of openings 37formed in he tube 31. The openings 37, in turn, communicate respectivelywith threaded bores 38 in the side wall of the shaft 30. The shaft 30further includes an annular, radiallyextending flange 39 disposedoutwardly (to the left, as viewed inFlG. 1) of the openings 36.

Similarly, formed in the right side of the shaft 30 is alongitudinally-extending bore within which is mounted a tube 4!. Thaannualr space between the tube 41 and the shaft 30 defines a passageway42 for the heavy liquid to flow out of the device 10. The space withinthe tube 41 defines a passageway 43 for the flow of light liquid intothe device 10. The tube 41 communicates with an inlet pipe 44 which is,in turn, coupled to a source of light liquid. An outlet pipe 45communicates with the passageway 42 and is coupled to a container or thelike to collect the heavy liquid effluent discharged from the device 10.The passageway 42 communicates, adjacent its inner end, with a set ofthreaded openings 46; and the passageway 43 communicates, at its innerend, with a set of openings 47 formed in the tube 41. The openings 47,in turn, communicate respectively-with threaded bores 48 in the sidewall of the shaft 36. The shaft 30 further includes an annular,radially-extending flange 49 disposed outwardly (to the right, as viewedin FIG. 1) of the openings 46.

The countercurrent exchange device also includes a rotor 60, which rotor60 is defined by a cylindrical outer shell 61 and a pair of annular endplates 62 secured at the outer ends thereof to the outer shell 61 bymeans of bolts 63. Formed centrally in each of the end plates 62 is anopening through which passes the shaft 30. The annular outer regions ofthe end plates 62 near the shaft 30 are secured respectively to theoutwardlyfacing surfaces of the flanges 39 and 49 by means of bolts 63.

A plurality of concentric cylindrical bands 64 is positioned in annulargrooves formed in the end plates 62 in a manner presently described,each band 64 being formed with a plurality of apertures 65. In the formillustrated, the bands 64 are arranged with the spacing between any pairthereof increasing as the radius increases. Although this is thepreferred form of construction, it is not necessary to the inventionhereinafter described.

Positioned in radially-aligned openings in the bands 64 is a supply tube66, which is threaded at one end thereof to mate with a threaded opening38 in the shaft 30. Additional sets of radially-aligned openings in thebands 64 accommodate additional supply tubes 66, all of which are, inthe form shown, in axial alignment. Each of the tubes 66 has an opening67 nearer the end thereof that is adjacent to the shaft 30. The outerend of each of the supply tubes 66 is located within a suitable openingin the shell 61, each of which openings has an enlarged, threadedportion to receive a plug 68. The plug 68 may be unscrewed to enableremoval of the tube 66, for cleaning or replacement. A supply tube 69passes through a second set of radially-aligned openings in the bands64. Additional sets of openings in the bands 64 accommodate furthertubes 69. Each supply tube 69 is threaded at one end thereof to matewith a threaded opening 48 in the shaft 30. Each tube 69 has an opening70 near the outer end thereof. The outer end of each of the supply tubes69 is located within a suitable opening in the shell 61, each of whichhas an enlarged threaded portion to receive a plug 71. A discharge tube72 passes through a third set of radiallyaligned openings in the bands64. Other discharge tubes are provided, each of which is threaded at oneend thereof to mate with the threaded openings 46 in the shaft 30. Eachof the tubes 72 has an opening 73 at its outer end, that is, adjacent tothe shell 61. The outer end of each of the tubes 72 is located within asuitable opening in the shell 61, which is enlarged and threaded toreceive a plug 74. Although two of each of the tubes 66, 69 and 72 areshown, it is to be understood that any number of such tubes may beprovided.

Referring now to FIGS. 3, 4 and 5 of the drawings, the details andconstruction of the bands 64 and the fluorocarbon sheeting appliedthereto will be described. Applied to the inwardly facing surface (thatsurface of each band 64 in FIG. 3 facing the bottom of the drawing) is asheet composed of a fluorocarbon material. Each of the sheets 80 has amultiplicity of apertures respcetively aligned with the apertures 65 inthe band 64. Passing through each pair of aligned apertures respectivelyin a band 64 and the adjacent fluorocarbon sheet 80 is a rivet 81 havingthe ends thereof deform ed, as is best shown in FIG. 4, into flanges 82,thereby securely to retain the fluorocarbon sheet 80 against itsassociated band 64. Each rivet 81 has passing therethrough an orifice 83for purposes to be explained hereinafter. A sheet 85 of fluorocarbon isalso applied to the inwardly facing surface of the shell 61 of the rotor60. The sheet 85 may be held securely in position by means of screws 86of the like.

in operation, heavy liquid from the source thereof is supplied throughthe inlet pipe 34, through the passageway 33, through the openings 37and 38 into the liquid supply tubes 66. The rotation of the rotor 60causes the heavy liquid to flow outwardly through the tubes 66 andthrough the openings 67 into the interior of the rotor 66. The heavyliquid flows outwardly through the orifices 83 in the rivets 81 bycentrifugal force. Similarly, light liquid from a source thereof flowsthrough the inlet pipe 44 and is supplied through the passageway 43, theopenings 47 and 43, and into the supply tube 69, all as indicated by thearrows. The centrifugal force of the spinning rotor 60 causes the lightliquid to flow outwardly through the tubes 69, as indicated by thearrows, and into the space between the two outermost bands 64. Thepressurized light liquid flows inwardly through the orifices 83 in therivets 81 and mixes with the heavy liquid in countercurrent fashion. Asthe liquids pass through the band 64, they are broken up into dropletsby the orifices 83. A violent and intimate mixing of bothdroplet-dispersed liquids then takes place in the areas between eachpair of bands 64,

- causing the solute in one liquid to be transferred to the solventwhich is the other liquid. After both liquids have passed through all ofthe mixing stages, the same continue on through the present nonmixing orclarification areas. The heavy liquid which arrives in the space nearthe outer shell 61 flows into the discharge tubes 72 by means of theopenings 73. The heavy liquid flows back down the tubes 72, as indicatedby the arrows, through the openings 46, the passageway 42, through theoutlet pipe 45 to a container for the effluent. The light liquid whichreaches the shaft 30 flows through the openings 36, through thepassageway 32, through the outlet pipe 35, as indicated by the arrows,and to a container for the light liquid effluent.

Generally, both liquids travel concurrently or in the same direction asthey pass through the rotor 60. This direction of travel is of coursethe same as the direction of rotation of the rotor itself. However, as aliquid passes from one band 64 to the next, this liquid is eitheraccelerated or decelerated as above described. Since the passage of aliquid from one band 64 to the next takes but a short moment of time,the described acceleration or deceleration thus imports a violent orjolting action to that liquid. In the case of the decelerating lighterliquid, the jolting action is in a direction opposed to the generaldirection of the liquids travel. On the other hand, the jolting actionof the accelerating heavy liquid is in the same direction as the generaldirection of the liquids travel. There thus occurs a violent'crosscollision between the two liquids in the area between any two bands 64.

The heavy liquid is thrown outwardly by the centrifugal force of thespinning rotor 60, against the inwardly facing surfaces of the bands 64.There may be solids in either the light liquid or the heavy liquid,which solids move outwardly with the heavy liquid and tend to adhere tothese inwardly facing surfaces of the bands 64. However, the presence ofa fluorocarbon sheet 80 on the inwardly facing surface of each band 64substantially reduces the quantity of such solids adhering to the bands.Because the solids are impelled outwardly by the centrifugal force, theyrarely have more than passing contact with the outwardly facing surfacesof the bands 64. Accordingly, the solids do not tend to adhere to theseoutwardly facing surfaces and there is no need for any fluorocarbonsheets to be attached thereon.

The size of the orifices 83 are selected to maximize the efficiency ofthe device for the particular liquids being used. The size of eachorfice may be anywhere from one-sixteenth inch to five-eighths of aninch in diameter. The orifices 83 may be constant in size or gradateeither radially outwardly or radially inwardly. Whatever small amountsof solutes do adhere to the fluorocarbon sheets are loosely held therebyand can bands 64, only a few rivets 81 are required. The centrif-.

ugal force created by the spinning rotor 60 will operate to presstightly the sheets against their associated bands 64. A preferable formof fluorocarbon is polytetrafluoroethylene, since it has great strengthand ability to withstand the corrosive tendency of certain liquids whichmay be used.

This construction can be used with the very best corrosion-resistantstainless steel such as type 3l6 previously referred to. This, by virtueof the fact that the fluorocarbon sheets 80 are applied to the bands 64and secured thereto by rivets rather than applying by way of a spray andthen heating the bands to solidify the spray.

Although the specific embodiment shown in the drawings is a centrifugalcountercurrent exchange extractor, it is to be understood that theinvention is equally useful in a centrifugal separator. In such a case,only one set of distribution tubes is needed, to admit the liquidcontaining two phases which'are to be separated. The point along theradial extent of each distribution tube which the liquid is to beadmitted into the rotor, would be dependent upon the ratio of the heavyphase to the light phase. A plurality of cylindrical, concentric,apertured separator bands are provided, which bands function ascoalescent areas to assist in the separation process. It should furtherbe noted that the centrifugal countercurrent device 10, illustrated inthe drawings can be converted into a separator, by blocking one set ofdistribution tubes.

While a preferred embodiment of the invention has been shown anddescribed for illustrative purposes, it will be understood that variousmodifications may be made therein, and it is intended to cover in theappended claims all such modifications as fall within the true spiritand scope of the invention.

We claim:

1. A centrifugal device comprising a shaft, a rotor carried by saidshaft and having a cylindrical shell, a plurality of radially spacedcylindrical apertured bands mounted in said rotor, a plurality ofcylindrical fluorocarbon sheets respectively against the inwardly facingsurfaces of as least some of said bands, each of said sheets havingapertures therethrough which are respectively aligned with the apertureson the adjacent one of said bands, and a plurality of rivetsrespectively passing through at least some aligned apertures on saidbands and said sheets and deformed to secure firmly said sheets to saidbands, and rivets each having an orifice for the countercurrent flow ofliquids therethrough.

2. The centrifugal device of claim 1, wherein said rivets pass throughall of said aligned apertures.

1. A centrifugal device comprising a shaft, a rotor carried by saidshaft and having a cylindrical shell, a plurality of radially spacedcylindrical apertured bands mounted in said rotor, a plurality ofcylindrical fluorocarbon sheets respectively against the inwardly facingsurfaces of as least some of said bands, each of said sheets havingapertures therethrough which are respectively aligned with the apertureson the adjacent one of said bands, and a plurality of rivetsrespectively passing through at least some aligned apertures on saidbands and said sheets and deformed to secure firmly said sheets to saidbands, and rivets each having an orifice for the countercurrent flow ofliquids therethrough.
 2. The centrifugal device of claim 1, wherein saidrivets pass through all of said aligned apertures.